Field of the Invention
The present invention relates to a sheet feeding apparatus applied to an image forming apparatus, such as a facsimile machine, a copier, and a printer, and relates to an image forming apparatus provided with the sheet feeding apparatus.
Description of the Related Art
An image forming apparatus, such as a facsimile, a copier, and a printer, a sheet feeding apparatus, such as a document feeding apparatus and a manual paper feeding apparatus, which feeds stacked documents and recording media (hereafter, “sheets”). A sheet feeding apparatus provided with a leading end positioning member (a sheet regulating unit) for positioning leading ends of a bundle of sheets stacked on a tray is proposed (U.S. Pat. No. 6,547,235).
When a sheet bundle is stacked on a tray, the position of the leading end positioning member is regulated and is fixed by a stopper. A leading end of the sheet bundle is made to abut against the leading end positioning member on the tray to position the leading end of the sheet bundle. The sheet bundle positioned on the tray is fed by a pickup roller. When a sheet is fed by the pickup roller, regulation of the leading end positioning member by the stopper is released and the leading end positioning member is pressed and moved by a sheet fed by the pickup roller.
An exemplary operation of the leading end positioning member is described. The pickup roller is provided to be movable up and down between a feeding retracted position where the pickup roller is separated from the sheet bundle and a feeding position where the pickup roller abuts against an upper surface of the sheet bundle to feed the sheet. When the pickup roller is located at the feeding retracted position, the leading end positioning member engages with the stopper, whereby the leading end positioning member is in a fixed state in which movement is regulated. In the state where the leading end positioning member engages with the stopper and movement of the leading end positioning member is regulated, the leading end of the sheet bundle is made to abut against the leading end positioning member and is positioned on the tray.
When the pickup roller is moved downward from the retracted position to the position where the pickup roller abuts against the upper surface of the sheet bundle on the tray and feeds the sheet, engagement between the leading end positioning member and the stopper is released. This state is a fixing released state where the leading end positioning member is movable. When the pickup roller rotates to feed the sheet, the leading end positioning member is pressed by the fed sheet and the sheet is sent to the downstream.
In a related art configuration, when the sheet bundle is made to abut hard against the leading end positioning member on the tray, the leading end positioning member and the stopper may engage each other excessively firmly, and releasing thereof may be difficult. If the engagement is not released, the leading end positioning member is left in a fixed state in which the movement is regulated by the stopper. Therefore, if the pickup roller feeds the sheet, the fed sheet is disturbed by the leading end positioning member of which engagement is not released, thereby causing a jam.